A simple system of swept source optical coherence tomography for a large imaging depth range

In swept source optical coherence tomography (SSOCT), the imaging depth range sometimes limits its application, such as the whole eye measurement. The methods of extending depth range usually need to redesign the system or add some additional devices. In this paper, we propose a simple system of SSOCT for a large imaging depth range. The system is the same as the original SSOCT with using the swept source clock signal except for a slice glass in the reference arm. The large depth range is achieved by increasing the number of sampling point in every spectrum and wavenumber calibration. More sampling points can be obtained by high speed acquisition mode. Since the swept source clock signal cannot be used in this mode, the internal clock from the analog-to-digital converter is used as trigger signal and the OCT imaging signal is acquired with uniform time interval at a 1GS/s sampling rate. The wavenumber calibration is carried out with a reference signal generated by using the slice glass. Compared with the results of the clock signal calibration, the performance of the wavenumber calibration is demonstrated. The feasibility of the large imaging range is proved by a phantom experiment. The maximum imaging depth range is over 7mm, which is 1.9 times larger than that of the original SSOCT system. Imaging of an in-vivo goldfish eye is conducted. The anterior and retina segments are obtained simultaneously, which cannot be achieved with the original SSOCT system. Experimental results demonstrate that the imaging depth range can be effectively extended with the system.